Wednesday, January 30, 2008

There are benefits to living in the frozen tundra we call Minnesota! This is a picture of a sundog taken in NE Rochester last week. We could see it from our office window. They are really beautiful. For a mini-science lesson on sundogs, see definition below... A sundog (also called a parhelia) is a rainbow-like spot in a cirrus cloud. Light shining through ice crystals in the cloud makes a sundog, much like light shining through raindrops makes a rainbow. They are reddish on the side facing the sun and often have bluish-white tails stretching horizontally away from them.

Cirrus clouds--those high fleecy white bands or patches in the sky--are mostly tiny particles of ice. Ice can take on many forms and shapes. The cloud ice, however, is shaped like hex bathroom tiles or stubby pencils each no bigger than the tiniest grains of sand. These ice crystals bend light like a prism, disperse its colors, and cause sundogs.

When the crystals line up like tiles on a table, the light shining through makes sundogs. The horizontal crystals bend the light 22 degrees as the light enters and exits the crystal. Light colors fan out from the bending and display as a sundog. Sundogs are among the most commonly seen sky phenomena, appearing most prominently when the sun is low.

They usually appear in pairs two handbreadths on either side of the sun when it rises or sets behind a very thin veil of high cirrus clouds. Hold your arms straight out to estimate the two handbreadths.

2 comments:

  1. My Mom always used to say when there is a sun dog that means it really really cold....I think she's right, Brrrrrrrrrr
    Great picture :)

    ReplyDelete
  2. beautiful and a beautiful picture.

    ReplyDelete

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